Racks really need stable room temps and typically 80ºF is what is best just heat the room to 80 and hold it there and the issue is gone. The point is often missed by people whom recommend using racks that most how do have them have rooms at 80ºF and 60% humidity. The problem with out this is there is very few ways to control the cool side and ambient air temps by far the easiest way is to heat the room and hold it at constant temps most use a t-stat with an oil filled heater.